Spark plug



Jan. 30, 1934. A. E. ANDERSON 1,945,408

SPARK PLUG Filed April 11, 1952 Patented Jan. 30, 1934 UNITED STATESPATENT OFFICE 1 Claim.

My invention relates to a spark plug having the spark gap placed withinan insulated chamber, so as to prevent any of the high voltage currentfrom being attracted to any grounded part of the spark plug or othergrounded part of the engine, except through the spark gap to thegrounded electrode of the spark plug.

Another object of my invention is to place the spark gap so as to keepthe same and the electrodes out of the compressed charge of thecombustion gases as much as possible. The reason for this is obviousbecause a compressed charge will act more or less as a conductor to thehigh voltage current and thereby weaken the spark at the gap. This isbest proven when starting a cold motor with the choke out. Under thiscondition the compressed charge becomes equivalent to a solid conductorwhich causes the motor to miss.

Still another object of my invention is to construct a plug in such amanner that it will be unafiected by the different temperatures that maybe found in various combustion engines while the gap and electrodes arewell protected by means of the insulation chamber so that thepre-ignition is at a minimum. The porcelain insulator is so constructedthat an annular space is formed around it where the ground electrodepasses through, which space is large enough to allow the groundedelectrode to expand.

This arrangement of the electrodes and insulated chamber differs fromthe spark plugs that have been used in the past, where no considerationwas given to the spark gap being exposed and directly projecting in thepath of the compressed charge of gas in the cylinder.

It is also obvious that a spark gap placed in an insulated chamber, asis clearly shown in the drawing, will have the advantage over the oldstyle spark plugs when the gap is placed below the insulated part ofcenter electrode, in that the resistance at the gap is cut down, therebygiving a hotter spark at all times and chances of fouling becomes aminimum.

In the accompanying drawing, one embodiment of my invention is shown andFig. 1 is a vertical axial section of the spark plug and Fig. 2 ahorizontal section along line 2-2 of Fig. 1.

In the drawing, reference numeral 10 represents the metal body orhousing of the plug and 12 the porcelain insulator or dielectric coremember fitting closely in the hollow space formed in said body. Thedielectric has an upwardly tapering shoulder 20 merging into the neckportion 21 extending through the central opening formed in the securingnut 11, which engages the shoulder 20 and is preferably threaded in theplug body as at 22.

The dielectric has also a downwardly tapering shoulder 23 terminatingwith a narrow shank 24 stopping short of the lower externally threadedend 19 of the body, which in the usual manner screws into the cylinderhead of the internal combustion engine.

Around the shank 24 of the dielectric is formed an annular space 14 inthe lower end 19 of the metal body to permit expansion and cooling. Inthe lower end or shank 23 is provided a downwardly open, small chamber13 into which projects the free end of the electrode 15 which runs inaxial direction completely through the dielectric or porcelain insulator12 engaging with the leading in wire 16 clamped in position by the screwcap 17.

The ground electrode 18 is secured in the threaded end 19 of the bodyand runs in radial direction therethrough and across the annular space14, through the dielectric shank 24 and projects with its spark pointinto the chamber 13 so as to form the spark gap 25 between its point andthe point of the axial terminal 15.

It will thus be seen that, because the spark gap is located within thechamber 13, the ends of the terminals are not exposed to the hot flameor combustion gases and will, therefore, not wear away as is usual withother spark plugs. Furthermore, because of the annular chamber 14, notonly the shank 24 of the dielectric but also the ground electrode willfind room for expansion.

I claim:

In a spark plug the combination of a hollow metal housing and adielectric core member seated therein, oppositely directed upper andlower shoulders on the core member and housing respectively, adapted tomake firm connection between them, a narrow shank at the lower end ofthe core member having a downwardly open chamber, an annular space beingformed around said shank in the housing, a main electrode carried by thecore member projecting with its spark point into said chamber, and aground electrode secured in the threaded portion of said housing andextending across said annular space through said shank and projectingwith its spark point substantially radially into said chamber, thusforming with the point of the main electrode a spark gap within saidchamber, said shank and electrodes having room for expansion within saidannular space.

AUGUST E. ANDERSON.

